Having returned to turning for the first time since school, (many years ago)
and have managed to full our house with many small bowls, hollow forms,
couple of lamps, pens, and some thin platters etc. using up all my hoarded
timber.
Four months into this renaissance, I have recently started to spot my work
pieces "wobbling" whilst spinning, made very apparent when attempting to cut
a 4 x 1mm groove and inset a contrasting band near the rim of a part-turned
(outside only) 8" sycamore bowl blank (faceplate mounted), and was even more
apparent when reversed and "chucked"
The lathe, tools and my current experience are all four months old, and the
"wobble" seems progressive. The lathe bearings, and the chuck have just been
checked by the supplier (Axminster) and found to be well within tolerance.
Thus they have decided, the problem is me!
Any help, what am I doing wrong?

Phil Johnson wrote:
I have recently started to spot my work
pieces "wobbling" whilst spinning, made very apparent when attempting to cut
a 4 x 1mm groove and inset a contrasting band near the rim of a part-turned
(outside only) 8" sycamore bowl blank (faceplate mounted), and was even more
apparent when reversed and "chucked"
Any help, what am I doing wrong?

You say the blanks are faceplate-mounted, and that the wobble is
progressive. it sounds as though the mounting is getting looser as you
turn the blank. If the blank is screwed to the faceplate, double check
the screws. If you are using a sacrificial blank between the faceplate
and the turning blank, see if it is getting loose.
Good luck,
Dave in Fairfax
--
reply-to doesn't work
use:
daveldr at att dot net

Is it possible that the connection of the lathe to the bed is a source of
trouble?

Derek

Thankyou gentlemen,
Have checked headstock to lathe, I'm 14stone odd and can't move it when
tightened, and have tried two different faceplates with long and short #8's
in an attempt to isolate the problem
The lathe (M900) has a home made shelf under with 50k of cement in bags (a
hint from this newsgroup) and is rawbolted to a concrete (bloody cold) slab
floor.
Even turning small items I can see the eccentricity.

Phil

"Derek Hartzell" wrote in message
...
Is it possible that the connection of the lathe to the bed is a source of
trouble?

Derek

Given that you have checked all this, I would recommend you change the
bearings.

I once heard of an car or airplane component sourced from two different
countries. The one lasted several times as long as the other. Both were
within tolerances. The longer-lasting one, however, seemed to have all
parts machined with no detectable variability with the accuracy of gauges,
while the other varied, but all within specs. Maybe the bearings are
wearing and while "within specs" they are causing vibration.

Also, when remounting in the chuck, have you tried rotating the piece in the
chuck a quarter turn at a time, tightening and spinning under power until
you get the lowest deflection/vibration mounting?

Derek

Phil;
Is there a possibility that the headstock lathe spindle is bent? A bowed
shaft would give those symptoms. It is possible to bow a lathe spindle by
over tightening a pulley set screw - if the pulley hole is irregular. I had
a lathe once with this problem (huge flat belt cast pulley with uneven
center hole). Check to see if the spindle is bent.
Jim

--
James P. Riser
Http://www.JamesRiser.com

Phil, have you recently tightened the rawlbolts and inadvertently warped
& twisted the lathe bed? Does the wobble disappear after you true a
sacrificial block attached to a faceplate? Do you put too long a tenon
or dovetail on the blank for the chuck to center & hold? Does a M900
have a rotating headstock? Diagnosis is usually difficult---treatment
often easy. Arch

Fortiter,

I'll go another direction.

With the lathe off, rotate the piece with the toolrest up close. Look at the
gap - Is there one close approach point or two?

If one, pursue mounting problems.

If two, take a look at a couple of wild ideas.

If two, diametrically opposed, and on the endgrain, what you have is a
natural result of releasing the tension of the wood by hollowing it.

What you must do is either go inside to outside and back again when
hollowing, realizing that you will be causing substantial risk to the
turning as it gets thinner, or use a bowl steady to help maintain
circularity until the hollowing is complete.

Wild idea number two, which is suggested by your remark that an unhollowed
(unhallowed?) piece wobbles. It could be that you're riding the tool on the
piece versus steadying it on the toolrest and letting the wood come to it.
What happens here is the tool dives into the face grain and climbs into the
end grain. This is often accentuated by sanding with the paper supported on
the work, as you can easily sand the face, but end grain only with
difficulty.

"Phil Johnson" wrote in message
...
Having returned to turning for the first time since school, (many years
ago)
and have managed to full our house with many small bowls, hollow forms,
couple of lamps, pens, and some thin platters etc. using up all my hoarded
timber.
Four months into this renaissance, I have recently started to spot my work
pieces "wobbling" whilst spinning, made very apparent when attempting to
cut
a 4 x 1mm groove and inset a contrasting band near the rim of a
part-turned
(outside only) 8" sycamore bowl blank (faceplate mounted), and was even
more
apparent when reversed and "chucked"
The lathe, tools and my current experience are all four months old, and
the
"wobble" seems progressive. The lathe bearings, and the chuck have just
been
checked by the supplier (Axminster) and found to be well within tolerance.

Thus they have decided, the problem is me!
Any help, what am I doing wrong?

Phil Johnson wrote:

Four months into this renaissance, I have recently started to spot my work
pieces "wobbling" whilst spinning, made very apparent when attempting to cut
a 4 x 1mm groove and inset a contrasting band near the rim of a part-turned
(outside only) 8" sycamore bowl blank (faceplate mounted), and was even more
apparent when reversed and "chucked"

You mentioned that you used up all your hoarded timber. Are you now turning
"green" wood? If turned thin without allowing the wood to try it will warp
causing a wobble.

--
Jack Novak
Buffalo, NY - USA
(Remove "SPAM" from email address to reply)

Axminster have dial tested my headstock bearing and they are within
tolerance ending any warranty discussion.
Derek, I did try the faceplate adaptor on the chuck, no wood, seemed ok
(visually) after re-seating in a couple of different positions, and clearing
the recess of any small wood particles
The headstock does rotate and whilst I have to be careful with alignment for
between centres turning, (+/- a lot)on faceplates/chucks etc. when tightened
(not quite broken tight) I can't move it..
Arch, I did check and re-tighten my rawbolts, and all four had relaxed a bit
in the short time since having the lathe, and subsequently tried any bit of
wood, turned to almost nothing, seems to exhibit the same eccentric
(visible) motion. I do tend to make the chuck recess deeper when compared to
pro turners bowls at local craft fair/shops etc, to err on the safer side of
ignorance I thought.
James, I have no way at home of checking the straightness (I think) of the
headstock shaft, but would hope that the supplier had done that when I took
the motor/headstock assembly in for testing.
Jack, the last bowl blanks were "shop bought" from local wood turning supply
retailer, "part seasoned" I'm told, they look and feel dry after turning off
the wax.
George, in two positions relative to the toolrest, 180 degrees apart, so is
it me, am I riding the bevel harder than securing the gouge to the tool
rest, would that cause this ovality. And I do have some difficulty removing
torn grain during final sanding, seems to take forever no matter how little
there is of it.

Phil (with thanks to all)


"Derek Hartzell" wrote in message
...
Given that you have checked all this, I would recommend you change the
bearings.

I once heard of an car or airplane component sourced from two different
countries. The one lasted several times as long as the other. Both were
within tolerances. The longer-lasting one, however, seemed to have all
parts machined with no detectable variability with the accuracy of gauges,
while the other varied, but all within specs. Maybe the bearings are
wearing and while "within specs" they are causing vibration.

Also, when remounting in the chuck, have you tried rotating the piece in
the
chuck a quarter turn at a time, tightening and spinning under power until
you get the lowest deflection/vibration mounting?

Derek

Sounds likely.

Rather than "ride," try to "guide" the bevel, and you'll begin your sanding
in a better state.

I use a flexible shaft powered by a washing machine motor to sand. That
way I can rest the handle of the shaft on the toolrest to steady, rather
than referencing the disk on the work. Double benefit, really, as I don't
have to press, thereby aggravating the natural tendency to sand faster in
soft face (or spalt), slower in end grain. Heat is also the enemy in
sanding. It hardens and burnishes the surface, and the tears are more
obvious by comparison. If you're able to kiss, rather than press the work,
you'll have less heat. If you do start to burnish the work when sanding,
don't do what seems natural and press harder. Stop, wet the shiny areas to
break the hardening, then return after the surface looks dry.

Take a peek at my weird technique, which involves running the gouge with the
angle of attack parallel to centerline.


"Phil Johnson" wrote in message
...
George, in two positions relative to the toolrest, 180 degrees apart, so
is
it me, am I riding the bevel harder than securing the gouge to the tool
rest, would that cause this ovality. And I do have some difficulty
removing
torn grain during final sanding, seems to take forever no matter how
little
there is of it.

A remote diagnosis is difficult, but if your spindle is within tolerances
but you are eccentric, then the problem may be the mating surfaces between
your spindle and the faceplate. Mounting the faceplate "true" on the spindle
does not come from the threads but from the mating surface on the spindle
and the mating surface on the faceplate.

It is easy to check the mating surface on the spindle. If ok, mount the
faceplate and check the faceplate for runout. You may have warped or bent
your faceplate. It is easier than you think to do this with screws,
especially if you use a ratchet for leverage.

"Phil Johnson" wrote in message
...
Having returned to turning for the first time since school, (many years
ago)
and have managed to full our house with many small bowls, hollow forms,
couple of lamps, pens, and some thin platters etc. using up all my hoarded
timber.
Four months into this renaissance, I have recently started to spot my work
pieces "wobbling" whilst spinning, made very apparent when attempting to
cut
a 4 x 1mm groove and inset a contrasting band near the rim of a
part-turned
(outside only) 8" sycamore bowl blank (faceplate mounted), and was even
more
apparent when reversed and "chucked"
The lathe, tools and my current experience are all four months old, and
the
"wobble" seems progressive. The lathe bearings, and the chuck have just
been
checked by the supplier (Axminster) and found to be well within tolerance.
Thus they have decided, the problem is me!
Any help, what am I doing wrong?

thankyou, I do (did use) a power driver to run-in the screws through the
stock cast faceplate supplied with the lathe, but for the last couple of
bowls I used a new steel faceplate chuck adaptor, and noticed the same level
of perceived movement. Even on a small blank, say 4 x 2" I struggle to get
it square to the axis of rotation and worse when reversed and chucked for
hollowing.

"Ralph Heasley" wrote in message
...
A remote diagnosis is difficult, but if your spindle is within tolerances
but you are eccentric, then the problem may be the mating surfaces between
your spindle and the faceplate. Mounting the faceplate "true" on the
spindle
does not come from the threads but from the mating surface on the spindle
and the mating surface on the faceplate.

It is easy to check the mating surface on the spindle. If ok, mount the
faceplate and check the faceplate for runout. You may have warped or bent
your faceplate. It is easier than you think to do this with screws,
especially if you use a ratchet for leverage.

"Phil Johnson" wrote in message
...
Having returned to turning for the first time since school, (many years
ago)
and have managed to full our house with many small bowls, hollow forms,
couple of lamps, pens, and some thin platters etc. using up all my
hoarded
timber.
Four months into this renaissance, I have recently started to spot my
work
pieces "wobbling" whilst spinning, made very apparent when attempting to
cut
a 4 x 1mm groove and inset a contrasting band near the rim of a
part-turned
(outside only) 8" sycamore bowl blank (faceplate mounted), and was even
more
apparent when reversed and "chucked"
The lathe, tools and my current experience are all four months old, and
the
"wobble" seems progressive. The lathe bearings, and the chuck have just
been
checked by the supplier (Axminster) and found to be well within
tolerance.
Thus they have decided, the problem is me!
Any help, what am I doing wrong?